1. Field of the Invention
This invention relates to an artificial lattice film having high magnetic resistance ratio (MR ratio) and a magneto-resistance effect element using such an artificial lattice film.
2. Description of the Related Art
Magneto-resistance effect devices (elements) for detecting magnetic field by using magneto-resistance effect are extensively used at present as magnetic sensor, magnetic head, rotation detecting device, position detecting device, and the like.
Permalloy generally mentioned as material to exhibit magneto-resistance effect has small anisotropic magnetic field of the order of 4 Gauss, and indicates very satisfactory soft magnetic characteristic. For this reason, in the field of magnetic recording, permalloy is suitable for material for MR head which reads out very weak signal magnetic field.
However, in order to cope with high density magnetic recording forecasted or predicted to be further developed in Future, material having larger MR ratio is required.
In an artificial lattice film as multi layered film made up so that magnetic layers consisting of Fe and conductive layers consisting of Cr are successively stacked one after another, MR ratio of about 50% was observed under the condition of low temperature of 4.2K and magnetic field 2 T, and the spot light of attention on this observed result was focused (M. N. Baibich, et al; Phys. Rev. Lett. 61(1988)2472.).
Thereafter, in the artificial lattice film in which Co and Cu are respectively used as the magnetic layer and the conductive layer, in the case where there is employed, e.g., a multilayered structure of (Co 1.5 nm-Cu 0.9 nm).times.30 layers, MR ratio of 48% was observed under the condition of room temperature and magnetic field of 0.5 T. Moreover, in the case where a multilayered structure of (Co 1.5 nm-Cu 2 nm).times.30 layers is employed, MR ratio of about 19% was observed under the condition of room temperature and the magnetic field of 0.05 T (D. H. Mosca et al; J. Mag. Magn. Mat. 94(1991)L1.).
In order to obtain larger MR ratio, various artificial lattice films (film structures) were made up. However, since large external magnetic field is required, it is difficult to apply such artificial lattice film, e.g., as magneto-resistance effect element for magnetic recording. In addition, sensitivity was insufficient also as a magnetic sensor.
In view of the above, there has been proposed a method in which alloy including Fe, Ni, Co in combination is used in place of using Fe or Co by itself as the magnetic layer to thereby improve sensitivity with respect to external magnetic field. In the case where magnetic layer is constituted by alloy as described above, it is necessary to contain Co of 10% or more in order to obtain sufficient MR ratio. However, when percentage content of Co is high, coercive force is increased, resulting in the drawback that accuracy was low for use as, e.g., magnetic head or magnetic sensor.
As stated above, conventional artificial lattice films (film structures) were insufficient in the case they are used as magneto-resistance effect element for magnetic head or magnetic sensor.